With the development of wireless communication technologies for ensuring mobility, wireless communication systems with various standards have already been proposed and new wireless communication systems are being studied. A wireless communication system is designed to support user terminals accessing a core network through an air channel. That is, from the point of view of the end-to-end elements which are a service user and a service provider, it does not matter which standard is employed by a wireless communication system in using contents. Accordingly, a technique for maintaining a satisfactory condition of an air connection by enabling the performance of a seamless handover between different networks of different mediums is being studied.
There exists the Institute of Electrical and Electronics Engineers (IEEE) 802.21 Media Independent Handover (MIH) as a typical technique of handover between different networks. This is a vertical handover. According to the MIH standard, an MIH server, an MIH function (MIHF) of a mobile terminal (MT) and an MIHF of an access network are in existence to support a seamless vertical handover. Herein, the MIH server is an entity for collecting information on various networks and providing the information to the MTs. The MIHF is a function for exchanging commands and information for vertical handover, and is included in an MT and an access network respectively.
The vertical handover based on the MIH standard is performed as follows. If an MT recognizes that link condition with a serving network becomes worse, an MIHF of the MT accesses an MIH server and obtains information on neighbor networks. The MIHF of the MT scans candidate networks, selects a target network, and initiates the vertical handover. Hence, the MIHF of the MT requests a MIHF of the serving network to provide resource information of the candidate networks, and the MIHF of the serving network requests MIHFs of the candidate networks to provide resource information. Therefore, the MIHFs of the candidate networks check resource information, and provide the MIHF of the serving network with the resource information.
Herein, the resource information which is provided to the MIHF of the serving network from the MIHF of the candidate network is a Layer-2 (L2) resource information of a point of attachment (PoA) which is subordinated to the candidate network. The L2 resource information is information on the resource of a Media Access Control (MAC) layer, and is formed dependent on the network. However, the MIH is operative in a different layer from L2. That is, the MIHF may not collect the L2 resource information directly. However, a procedure that the MIHF of the candidate network collects the L2 resource information and provides the L2 resource information to the MIHF of the serving network has not been suggested. Therefore, it is necessary to suggest a way to exchange the L2 resource information between MIHFs.